Charting Young Stars’ Ultraviolet Light with Hubble

The Hubble Space Telescope’s Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) is a Director’s Discretionary program of approximately 1,000 orbits that will produce an ultraviolet spectroscopic library of young high- and low-mass stars in the local universe. The ULLYSES program will uniformly sample the fundamental astrophysical parameter space for each mass regime, including spectral type, luminosity class, and metallicity for massive stars, and the mass, age, and disk accretion rate in low-mass stars. The program is expected to execute over a three-year period, from Cycle 27 to Cycle 29.

The design and targets of these observations were selected in partnership with the astronomical community, allowing researchers from around the world to help develop the final program as well as have the opportunity to organize coordinated observations by other space- and ground-based telescopes. Staff at the Space Telescope Science Institute (STScI), in charge of implementing this project, will generate public data sets and provide technical support to ensure these data enable, support, and stimulate a broad range of transformative research. The sum of these collaborative efforts will be a unique ultraviolet legacy data set with lasting value.

The ULLYSES program was specifically selected to leverage HST’s unique ultraviolet capabilities in this area of research since both high- and low-mass stars feature different complex ultraviolet emission processes that strongly impact their surroundings and are difficult to model. The ultraviolet emission from star formation is central to a wide range of vital astrophysical problems, including cosmic reionization and the formation of planets.


Project Milestones

ULLYSES observations will be carried out over three cycles with periodic data releases as new observations are made.

Date Milestone
Fall 2019 Release of targets to the community
Spring 2020 First observations of massive stars in the Magellanic Clouds
Summer 2020 First data release and launch of external website
Fall 2020 First observations of low mass stars
Summer 2020 – Summer 2023 Quarterly data releases


Observing Strategies

Target Tables

westerlund galaxy

Who We Are


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